Method of reclaiming diamonds from industrial metal tools



Nov. 22, 1960 D. BREEsE ETAL METHOD OF RECLAIMING DIAMONDS FROM INDUSTRIAL METAL TOOLS Filed Nov. 10, 1958 %.m \mm .h lm Y United States Patent Office METHOD OF RECLAIMING DIAMONDS FROM INDUSTRIAL METAL TOOLS York Filed Nov. 10, 1958, Ser. No. 773,049

8 Claims. (Cl. 134-28) This invention relates to the method of reclaiming diamonds from industrial metal tools, and more particularly reclaiming diamonds from metal dies.

In the reclamation of diamonds from tools it has been the practice to cut away the tool around the diamond to allow the diamond to be removed therefrom. It has been found that such a method of reclamation was quite often damaging to the diamonds and the cutting tools used. In addition, this method was extremely time consuming and required a large amount of skilled labor.

An object of this invention resides in a new method of removing diamonds from metal mountings in tools by dissolving the metal from around the diamond.

Another object of this invention is an improved method for reclaiming diamonds from metal tools in a simple and economical manner which requires a minimum of personal attendance and skill.

With these and other objects in view, this invention contemplates a method for facilitating reclamation of diamonds wherein the diamonds are mounted directly in the tools or in a fused powdered metal mount within the tools. The tool is placed in a water solution and nitric acid is added to partially dissolve the fused powdered metal or other metal mounting from around the diamond to free the diamond from the tool body or casing. This nitric acid solution is heated to aid in the dissolving action. After the diamond is separated from the tool it is removed from the nitric acid solution and immersed in water to remove the nitric acid from the diamond. Thereupon the diamond is placed in another water container. Hydrochloric acid is added to the container and heat is applied thereto to cause the solution to boil. This solution acts to remove impurities from the surface of the diamond. The diamond is then placed in a water solution to remove the hydrochloric acid from the diamond.

Other objects, advantages and novel features of the invention will become apparent when considered in conjunction with the accompanying drawing wherein:

Fig. l is a view showing the diamonds and dies undergoing four progressive steps of the method;

Fig. 2 is a perspective view of a die showing the diamond mounted therein;

Fig. 3 is a cross-sectional view of the die of Fig. 2 showing the position of the fused powdered metal which holds the diamonds in place; and

Fig. 4 is .a cross-sectional view of the die of Fig. 2 after it has been processed, showing the fused metal partially dissolved in the area of the diamond with the diamond removed.

Refer-ring to Fig. 1 there is shown a table having supported thereon four liquid containers-25, 26, 27 and 28 representing four separate steps in applicants method. The containers and 27 have conventional electriC heating elements and 31, respectively, placed thereunder. The container 25 has a number of dies or tools ,"having diamonds mounted therein in fused powdered metal mountings 36 (Figs. 2-4), placed therein in a hot solution 37 of nitric acid and water. The container 26 has a number of the dies 35 and the diamonds 45 in a water bath 41. The container 27 has placed therein a number of the diamonds 45 in a hydrochloric acid and water bath 46 maintained in a boiling state by the heating element 31. The container 28 is supported directly on the table 20 and has placed therein a number of the diamonds 45 in a hot water bath 51.

To remove the diamonds 45 (Figs. 1-4) from the fused powdered metal 36 in the die 35, the dies are first placed in a Water bath in the container 25 .over the heating element 30 (Fig. l). A concentrated solution of nitric acid having a specific gravity of approximately 1.42 is then added to the water bath in the container 25 in suflicient quantity to create an active fizzing solution of nitric acid 37 to start the dissolving of the fused powderedmetal mounting 36 (Figs. 1-4) of the .die 35. Heat is then .applied to the nitric acid solution by the heat-ing element 30 to bring the temperature thereof to 100 F. or more, but appreciably below its boiling point to aid the dissolving action of the nitric acid solution. The fused powdered mounting metal 36 is porous and is therefore more susceptible to the action of nitric acid than is the hard die casing 38 of the die 35, which is usually made of stainless steel, Monel metal or the like. The fused powdered metal 36 is therefore dissolved at a much more rapid rate than is the die body 35. A plug 52, made of similar hard metal, originally used to compress the powdered metal to form the fused powdered metal mounting 3.6 when the diamond was mounted in the die casing 38 is similarly less susceptible to the action of the nitric acid.

Nitric acid is occasionally added to the solution 37 to maintain the active fizzing solution during the dissolying action. After three or four hours the fused powdered mounting metal 36 should be sufiiciently dissolved as shown at to allow the diamonds to drop out of the die casing 38 (Fig. 4). The dies 35 and the diamonds 45 are then removed from the nitric acid solution 36 and placed in the water bath 41 in the container 26 to remove the nitric acid from the dies 35 and the diamonds 45.

After the dies and diamonds are cleaned in the water bath in the container 26, the diamonds are immersed in water in the container 27 and hydrochloric acid is added to the solution to provide a solution 46, to remove impurities from the surface of the diamonds, which is approximately one part concentrated hydrochloric acid having a specific gravity of approximately 1.30 and one part water. Heat is added to the hydrochloric solution 46 in the container 27 to cause it' to boil to aid the impurity removal action of the solution.

After fifteen or twenty minutes in the boiling hydrochloric acid solution 46 the diamonds .45 are removed therefrom and placed in the water bath 51 in the container 28 to remove the hydrochloric acid therefrom.

The above-described method to remove diamonds I dissolve hard diamond supporting metal would be greater,

and because of the diamond to' metal boundary adjacent a the diamond; 7 It is to be understood that-the above'described arrangements are simply illustrative'of the application of the principles of this invention. Numerous other arrange: ments may be readily devised by those'skilled in the art 2,961,356 Patented Nov. 22, 1960 t which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. The method of reclaiming diamonds from members made of a metal selected from the group consisting of steel and Monel metal and having diamonds imbedded therein, which comprises treating such a member with a nitric acid solution, heating the nitric acid solution to at least 100 F. but below the boiling point of the nitric acid solution to dissolve metal supporting the diamond, and subsequently cleaning the diamond with hydrochloric acid.

2. The method of reclaiming diamonds from members each made of a metal selected from the group consisting of steel and Monel metal and having a diamond imbedded therein, which comprises immersing such a member in a water bath, adding concentrated nitric acid to the water bath to form a solution of nitric acid and to initiate dissolution of the metal supporting the diamond, heating the resulting nitric acid solution to at least 100 F. but below the boiling point of the nitric acid so as to free the diamond from the metal, subsequent-1y cleaning the diamond with hydrochloric acid and finally washing the diamond with water.

3. The method of reclaiming a diamond from a member made of a metal selected from the group consisting of steel and Monel metal and having a diamond imbedded therein, which comprises immersing the member in a nitric acid solution, heating the nitric acid solution to at least about 100 F. but below the boiling point of the nitric acid solution to dissolve metal supporting the diamond, Washing diamonds thus freed with water and subsequently cleaning the diamonds with hydrochloric acid.

4. The method for reclaiming a diamond from a diamond-holding metal member wherein the metal is selected from the group consisting of steel and Monel metal, which method comprises placing the member in a nitric acid solution, heating the nitric acid solution until the diamond becomes dislodged from the metal, washing the diamond with water, immersing the washed diamond in hydrochloric acid to remove impurities from the surface of the diamond and again washing the diamond with water.

5. The method for reclaiming a diamond mounted in a metal tool wherein the metal is selected from the group consisting of steel and Monel metal, which method comprises immersing the tool in a water bath, adding a concentrated nitric acid solution to the water bath to initiate dissolution of the metal mounting supporting the diamonds, heating the nitric acid solution during said dissolution to a temperature of at least about 100 F. but below the boiling point of said nitric acid solution, adding additional concentrated nitric acid to the nitric acid solution to maintain the concentration of nitric acid solution sufficient to continue dissolving the metal mounting during the dissolving step, washing resulting diamonds thus freed in water, immersing the diamonds in a second water bath, adding concentrated hydrochloric acid to said second water bath to initiate removal of impurities from the surface of the diamonds, applying suflicient heating during the removal of the impurities to cause the complete removal of said impurities by said hydrochloric acid, and finally washing the diamonds in Water.

6. The method for reclaiming diamonds each set in a tool body metal mounting wherein the metal is selected from the group consisting of steel and Monel metal, which method comprises the steps of immersing such a tool in a water bath, adding concentrated nitric acid to the water to form a solution of nitric acid and to initiate dissolution of the metal mountings, heating the nitric acid solution to a temperature of at leastabout 100 F. but below the boiling point of the nitric acid solution to cause metal of metal mountings to dissolve and free the diamond, washing the diamond thus freed in water heated at least to the temperature of the nitric acid solution to remove said nitric acid, immersing the freed diamond in a second water bath, adding concentrated hydrochloric acid to the water to provide a solution of at least one part of hydrochloric acid to one part of water so as to initiate the removal of impurities from the surface of the diamond, heating the hydrochloric acid solution formed to a temperature sufiicient to remove said impurities, and subsequently washing the diamond in hot water.

7. The method for reclaiming diamonds each set in a fused powdered metal die wherein the metal is selected from the group consisting of steel and Monel metal, which method comprises the steps of immersing such a die in a water bath, adding to the Water bath a concentrated solution of nitric acidhaving a specific gravity of at least about 1.42 to start a dissolving action on the fused powdered metal, heating the nitric acid solution formed to a temperature at least about F. but below the boiling point of the nitric acid solution so as to produce a dissolving action, continuing addition of concentrated nitric acid to the solution during the dissolving step until the diamond becomes dislodged from the die, removing the diamond from the nitric acid solution formed, washing the diamond in water heated at least to the temperature of the nitric acid solution, immersing the diamond in a second water bath, adding concentrated hydrochloric acid to the water bath until a solution of at least one part of hydrochloric acid having a specific gravity of about 1.30 with one part of water is formed, said second bath serving to remove impurities from the surface of the diamond upon heating, heating the hydrochloric acid solution formed at least to the temperature of the nitric acid solution during the removal of impurities, and subsequently washing the diamond in water also heated to at least the temperature of said nitric acid solution.

8. The method for reclaiming diamonds set infused powdered metal die centers wherein the metal is selected from the group consisting of stainless steel and Monel metal, which method comprisesimmersing a plurality of such dies in a first water bath, adding to said water bath a concentrated solution of nitric acid having a specific gravity of at least about 1.42, heating the nitric acid solution formed to a temperature of at least about 100 F.

but below the boiling point of the nitric acid solution, coritinuing heating the dies in the nitric acid solution for at least three hours, adding additional concentrated nitric acid to the nitric acid solution for at least an additional three hours to maintain the dissolution action on the metal, whereby the diamonds are dislodged from the metal, removing the dislodged diamonds from the nitric acid solution, washing the diamonds in water heated at least to the temperature of the nitric acid solution, immersing the diamonds in a second water bath, adding concentrated hydrochloric acid to the water bath to provide a solution of at least one part of hydrochloric acid having a specific gravity of about 1.30 to one part of water for at least about 15 minutes to remove impurities from the surface of the diamond upon heating, heating the hydrochloric acid solution formed during the removal of the impurities to at least the temperature of the nitric acid solution to aid in the removal action, and subsequently washing the diamonds in water also heated at least to the temperature of said nitric acid solution.

References Citedin the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF RECLAIMING DIAMONDS FROM MEMBERS MADE OF A METAL SELECTED FROM THE GROUP CONSISTING OF STEEL OF MONEL METAL AND HAVING DIAMONDS IMBEDDED THEREIN, WHICH COMPRISES TREATING SUCH A MEMBER WITH A NITRIC ACID SOLUTION, HEATING THE NITRIC ACID SOLUTION TO AT 